Gulp

I started off just switching things to gulp as I said I would in #16, but then I went ahead and made a couple of other changes too. I normally would make separate PRs from separate branches but these other changes depend on the first PR anyway.

Other things include renaming "nw-desktop-notifications", etc. to "nodeifications" everywhere, checking in the bower dependencies and noting in the readme that nodewebkit >=0.9.2 is required.